Radioactive materials are prohibited in international mail and domestic mail if required to bear the DOT Radioactive White–I, Radioactive Yellow–II, Radioactive Yellow–III label,or the Fissile label (49 CFR 172.436, 172.438, or 172.440, respectively) or if it contains quantities of radioactive material in excess of those authorized in 347. Radioactive materials are prohibited in domestic mail via air transportation. For international mail, the standards in IMM 135.5 apply.

A white package label bearing the French words “Matieres Radioactives” (Radioactive Materials) must be securely affixed, taped, or gummed to the address side of each mailpiece containing radioactive materials. The sender is responsible for supplying and affixing this label to the mailpiece.

The address side of the mailpiece must clearly display the following marking: “This package conforms to the conditions and limitations specified in 49 CFR 173.421 for radioactive material, excepted package–limited quantity of material, UN2910 and is within Postal Service activity limits for mailing.”

The address side of the mailpiece must clearly display the following marking: “This package conforms to the conditions and limitations specified in 49 CFR 173.424 for radioactive material, excepted package–instruments or articles, UN2911 and is within Postal Service activity limits for mailing.”

The address side of the mailpiece must clearly display the following marking: “This package conforms to the conditions and limitations specified in 49 CFR 173.426 for radioactive material, excepted package–articles manufactured from natural uranium (or natural thorium), UN2909 and is within Postal Service activity limits for mailing.”